Endocrine Abstracts

Introduction: Pituitary insufficiency is a late-onset sequel of cranial irradiation for nasopharyngeal tumors. In a Cancer Survivor Study, 43% of patients treated for nasopharyngeal tumors had one or more endocrinopathies. We aim to characterize the pituitary-related outcomes following cranial radiotherapy for nasopharyngeal tumors over a period of 5 years.

Material and methods: The effects of cranial irradiation on hypothalamic-pituitary function were studied first after a mean time post-radiation of 3.66±2.91 years than controlled after 3-year period in 13 patients (7 men and 5 women) with nasopharyngeal carcinoma of a mean age 31.08±14.40 yo. No preradiation endocrinopathies were noted. The estimated radiotherapy doses were 68.91±7.26 Gray. The diagnosis of pituitary hormone dysfunction was based on standard criteria. Specifically, GH deficiency if a peak stimulated GH level was <10 ng/ml after the sequential administration of 2 secretagogues. Central hypothyroidism was diagnosed if the patient had a low free thyroxine value in the setting of a normal level of thyroid-stimulating hormone (TSH). Central adrenal insufficiency was diagnosed if a patient had a peak stimulated cortisol level of <18 μg/dl after low-dose (1 μg) adrenocorticotropic hormone (ACTH) stimulation testing. Hypogonadotropic hypogonadism was diagnosed if patients had absence of puberty by age 13 years in girls and age 14 years in boys with low serum gonadotropin levels. Data are reported as means±S.D.

Results: Of the 13 patients who had received radiation therapy after 3.66±2.91 years of radiotherapy treatment, 38.46% have at least one central endocrinological impairment. Significant impairment in the secretion of growth hormone (23.07%), gonadotrophins (15.38%), corticotrophin (7.6%) and thyrotropin (7.6%) were evident and 30.7% of patients developed hyperprolactinemia. Growth hormone deficiency was the earliest endocrine dysfunction observed. The cumulative probability of endocrine dysfunction was estimated to be 62% after a mean of 5 years with deficiencies in growth hormone, gonadotrophins, corticotrophin and thyrotropin found in 84.6%, 61.53%, 53.8%, and 38.46% of patients. Hyperprolactinemia was uncommon in the male patients (23.07%) but occurred significantly more in four of five women within 5 years of cranial irradiation.

Conclusion: Thus, in these patients with no pre-existing disease in the hypothalamic-pituitary region, progressive impairment in hypothalamic pituitary function leading to endocrine dysfunction requiring treatment occurs in 62 per cent of patients 5 years after cranial irradiation. Regular endocrine assessment should be performed in all patients following cranial irradiation.